Dude all i can say is research research research... I researched for over a year about what my better options were, and only now am i going through with the engine swap in my car, basically turning it into a GTT. It is one hell of a pain in the ass, easiest option by far would be to sell and buy a GTT. Reasons I didnt do that are because the body of my car is in very good condition, and i have spent over $10000 in upgrading the brakes, suspension, body kit, paint, everything. So really the only thing i was missing was the GTT engine, gearbox and drivetrain; decided that if i was to start again and buy a stock GTT, i would be back to square one, where the only thing i liked about the car would be the engine, etc. and i would have to spend money everywhere else again. Also I am just very attached to my car
There is a thread on here about how to turbocharge your NA, have a read of that and also speak to N-DAWG and 666Dan as they have been through it themselves and gave me some good advice about it.
Before you go looking for more power though, have you upgraded your brakes and suspension? Because if you stinge on those things, your power upgrade will not be very much fun at all...
My 2c